1. Field of the Invention
The present invention relates to a sheet trimming apparatus for trimming a sheet bundle and an image forming system provided with this sheet trimming apparatus.
2. Prior Art
A high-speed image forming apparatus such as an electrophotographic image forming apparatus is connected with various types of optional devices. One of such optional devices is a sheet trimming apparatus that forms a plurality of sheets into a bundle which is then trimmed to align the ends of the sheet bundle.
The aforementioned sheet trimming apparatus is used as an optional device attached to the image forming apparatus, and therefore, is required to have a compact configuration.
The sheet trimming apparatus is required to dispose of the paper scrap separated from the sheet bundle by trimming. The compact sheet trimming apparatus uses a method of collecting the falling paper scrap into a paper scrap container.
The Patent Documents 1 and 2 employ a method wherein a paper scrap ejection chute is arranged in the space for a falling paper scrap, which is led into the paper scrap container.
Patent Document 1: Unexamined Japanese Patent Application Publication No. 2003-25759
Patent Document 2: Unexamined Japanese Patent Application Publication No. 2006-26754
As described above, the sheet trimming apparatus attached to the image forming apparatus is required to have a compact configuration. When it has a compact configuration, the space for the falling paper scrap is limited and the paper scrap may be jammed in the falling space. This problem has been left unsolved. In the Patent Documents 1 and 2, the angle of the chute is variable. It is variable in order to set the chute at the position that forms the falling space and at the position that does not form the falling space. The chute located at the position that forms the falling space is fixed.
As shown in FIG. 1, the paper scraps TS of various sheet widths V are produced due to the relationship between the sheet SA prior to trimming and the sheet SB (indicated by dotted lines) subsequent to trimming. What is called the sheet width V here is defined as the length of the paper scrap TS perpendicular to the edge E formed by trimming.
If the gap is reduced in the falling space where the paper scrap falls, the paper scrap may be jammed in the falling gap in some cases. Particularly the paper scrap TS of greater sheet width V tends to be jammed.
In the sheet trimming apparatus disclosed in the Patent Documents 1 and 2, the chute is fixed at a position for leading the falling paper scrap. This arrangement tends to cause the paper scrap to be jammed in the chute.